Upper-workspace and Bottom-workspace actions not working

Since upgrading to 4.20, the XFWM actions "Upper-workspace" and "Bottom-workspace" to switch vertically between workspaces aren't functioning for me. The shortcut keys are set in the configuration tool, and Left- and right-workspace still work fine, but up and down do nothing. I've tried changing the shortcut keys, but nothing works.

I have six workspaces arranged in two rows and the workspace switcher in my panel. I'm running on Arch with version 4.20.0-2. Thank you!